A comment left on my post about Chemical evolution ask me to comment about where did the initial energy came from for the Big Bang. I could have answered in a reply to his comment but the scope of the answers and the hypothesis I must explain to answer means it deserves a post of it own. I must say before I begin that prereionisation physics is not my field of research and that the ever more complex physics of the plank era (not to mention the “prebig bang physic) is probably beyond my understanding of physics. I will attempt to explain things but it will only be to the limit of my understanding and it could very well prove to be wrong.
Ok, first off do we need initial energy for the Big Bang, many would say yes because of the Law of Conservation of Energy. The problem is that a lot of people incorrectly interpret this law, it is though to mean something like Lavoisier law of conservation of matter: “Energy cannot be created or destroyed”. This is false, the law merely state that energy in a closed system must be conserved, i.e. that the sum of the energy present at any moment in the system remains a constant. I know, it sound like it’s exactly the same thing but it is not. The law of conservation of energy does not preclude the creation of energy provided that exactly the same amount of negative energy is created at the same moment. Up to a 1999 negative energy would get you laugh out of most scientific establishment but astronomer have discovered that such a kind of energy appears to exist in our universe in the form of the cosmological constant which produce an acceleration of the expansion of the universe. You might ask how this constant can be a negative energy, well it imposes a negative curvature on space while every other kind of energy impose a positive curvature on space. It has to be energy of opposite amplitude, i.e. a negative energy.
Now that we know that we can “create” energy, lets look at what could happen in a perfect vacuum, i.e. 0 energy, 0 space, 0 time. (the condition before the Big Bang). Well your 0 energy could spontaneously break into x part positive energy and –x part negative energy without any violation of conservation of energy. Once you have this separation of energy, many things could possibly happen, one of them would be the Big Bang (another would be annihilation of these energy to restore the vacuum state). Is it unlikely that the Big Bang would have occurred, yes and no. Yes because we do not know if a Big Bang event is likely and no because well if this is the explanation of the origin of the Big Bang it happen so the probability of it happening is 1. This hypothesis has at least one problem: the total energy of the universe has to be exactly 0, which doesn’t seem to be the case from our observation. But it does show that you do not absolutely need an energy field to have a Big Bang.
Another way to produce a Big Bang without requiring a preexisting energy would be through “quantum fluctuation”. Once again we must consider a vacuum where you have 0 energy, 0 space, and 0 time, now according to the quantum uncertainty Principe is you know the position exactly you can have “infinite” fluctuation of the momentum. Now, this uncertainty principle can also be used with energy and time. i.e. if you know the time exactly you have no idea of how much energy is involved. This could mean that their exist fluctuation in the vacuum state of energy of unimaginable proportion. Now, one of our theory for the origin of the universe stipulate that the Big Bang is a manifestation of the unwinding of 4 string to “create” the 4 known dimension (i.e. the 3 dimension of space +1 dimension of time). The energy requirement to unwind a string is staggering, as proven by the idea that no other string has begin unwind since the Big Bang. So imagine the situation, we have the vacuum state, fluctuating widely to follow our uncertainty principle one of those fluctuation reach the level of energy require to unwind the strings and Big Bang you get the universe with everything in it, the energy left over from the unwinding becoming the “positive” energy of the universe and causing the creation of matter.
A third way, more mysterious and I’d say esoteric way involve membrane theory. This production of the Big Bang implies that two (or more) multidimensional membranes collide with each other. This collision produces an interference pattern in a few dimensions that is observed by lower order dimensional being as being this universe. I must admit I am not very familiar with Membrane theory and it’s implication and construction (in fact you are close to have been shown the entirety of my understanding of the theory) but from what I know it can produce a Big Bang without an existing energy.
Of course there are hypothesis for the origin of the Big Bang that requires a preexisting energy level and various natural explanation for where this energy field came from (anything from tachyon moving back in time to the moment of the Big Bang to the rest state of vacuum to being a none zero level). Humanity understanding of anything before the reionisation of the universe (the cosmic microwave background) is sketchy because of the difficulty of having any observable. It’s understanding become purely theoretical when you approach the inflation era as the laws of physics start to leave the boundaries we know and understand. And finally it becomes almost purely conjectural when you reach the Plank epoch (before something like 10^-43 s after the Big Bang) when all our knowledge of physics fails. You can imagine what happen when you try to go into the condition before the Big Bang “when” its not even sure that physics works.
However, this can only be seen as an argument for a “god in the gap” i.e. we don’t know so it must be god. There are naturalist possibilities that do not involve supernatural intelligent or its intervention. These possibilities also respect one of the most interesting structures of physic the idea that there should be no discontinuity in the laws of physics. This means that at the boundaries between two laws (i.e. before and after the big Bang for example) the equation explaining both phenomenons must give the same answer. Since by definition god must be a discontinuity in the laws of physics any explanation involving him must be backed by much more evidence that: well we don’t know what does it.